This invention relates to a method for manufacturing plastic frameworks and a machine for carrying out machining operations that can be used with this method.
The use of four-head welding machines to form window frames and window sashes from elongate plastic sections is well known in the window manufacturing industry. This known machine, which welds the frames in a horizontal position, is capable of welding together two window frames at once in a preferred embodiment. After the frameworks have been welded, it generally is necessary to carry out certain machining and cleaning steps on the rectangular frames to prepare them for use as a window or sash. For example, it is commonly necessary to drill holes or to cut slots in the frames in order to prepare them for window hardware such as hinges and window opening mechanisms. Also, because there is generally excess weld material at the four corners of each frame as a result of the welding process, it is necessary to remove this excess plastic material and it is known to carry out this “corner cleaning process” by means of an automated corner cleaning machine. Further equipment, such as conveyors, can also be provided to move the welded framework from the welding machine to the machine or machines for carrying out machining and/or cleaning steps on the frames.
Despite the relatively high output of the known four-head welding machines that are capable of welding at least two window frames or sashes simultaneously, in the past corner cleaning machines have typically only been capable of cleaning one window frame or sash at a time. Also, the known conveying or feeding devices that have been used typically only transfer one frame at a time to the corner cleaning machine, which may also be capable of carrying out processing steps such as drilling required holes. Accordingly, there is a perceived need to speed up the window frame processing and window frame cleaning steps in the production line or equipment that is downstream from the four head welding machine. Although this could be accomplished by having two separate production lines for the window frames or sashes that receive the welded frameworks from the welding machine, this solution poses its own difficulties such as the requirement for an additional amount of floor space in the plant and the possible difficulty of matching up window frames or a window frame and a window sash that are to be sold together or that are to be connected to each other.
U.S. Pat. No. 6,086,703 issued Jul. 11, 2000 to Willi Sturtz Maschinenbau GmbH teaches a method and apparatus for manufacturing two plastic window frames at substantially the same time using a horizontal four-head welding machine: After at least partial cooling, the two welded window frames are released and removed. Special support elements located adjacent two of the welding heads are used for this purpose. The frames are moved out of the welding machine by means of a movable carriage on which two other welding heads are mounted. They are moved to an intermediate station on two conveyor belts located one above the other and then they are moved to a work station such as a bead cleaning machine.
Recent U.S. Pat. No. 6,006,408 issued Dec. 28, 1999 to Wegoma, Inc. teaches a window frame weld seam cleaner having a fixed support head and a movable support head. An inner conveyor belt moves a single window frame into and out of a first cleaning position for cleaning and machining the top corners of the window frame and into and out of a second cleaning position for cleaning and machining the bottom corners. The conveyor includes fixed and movable fences, table top back fences and clamps.
In applicant's co-pending U.S. patent application Ser. No. 10/716,344 filed Nov. 18, 2003 and entitled “APPARATUS AND METHOD FOR MOVING FRAMEWORKS BETWEEN WORK STATIONS”, there is disclosed a production line for manufacturing plastic frameworks such as window frames that includes a four-head automated welding machine capable of welding the four corners of two window frames, an optional processing machine for carrying out manufacturing steps on the welded frames and a corner cleaning machine. The line also uses clamping arm assemblies for moving the two plastic frameworks from the welding machine to the processing machine and then for moving the partially processed frameworks to the corner cleaning machine. The disclosure and drawings of this copending application are incorporated herein by reference. The disclosed method includes pulling partially cooled frameworks from the welding machine after they have been released from this machine along respective first and second pairs of horizontally extending guide rails using two gripper arm assemblies movably mounted on respective horizontally extending tracks. The first pair of guide rails is located above the second pair and the adjustable distance between the guide rails of each pair corresponds to an external dimension of the framework that is to be supported thereby. This pending patent application also describes a weld cleaning machine that is capable of carrying out processing steps as well on two plastic frameworks. Tools and knives are arranged on each side of this machine on a tools mounting plate which extends vertically and which can be moved vertically as required for carrying out the processing steps. In addition to weld cleaning knives mounted on movable knife holders, this machine can also be equipped with cutting tools and drilling unit assemblies.
According to one aspect of the present invention, it is an object of the invention to provide an improved machine for carrying out machining operations on a rectangular framework using at least one power tool, this tool being maneuverable in more than one direction in order to position it to carry out a number of machining operations.
According to another aspect of the invention, it is an object of the present invention to provide an improved apparatus for carrying out machining operations on plastic frameworks that employs a power tool that can be maneuvered in different ways in order to permit the tool to carry out different machining operations on a plastic framework, and that can be manufactured at a reasonable cost and in a way that makes the machine quite efficient and flexible.
According to a further aspect of the invention, it is an object of the invention to provide an improved method for processing plastic frameworks that includes forming two such frameworks in a welding machine and then moving these frameworks to a processing machine where processing steps can be carried out on the two frameworks by at least one power tool, the position of which can be changed to permit the tool or tools to carry out a variety of processing steps.
According to yet another aspect of the invention, it is an object of the invention to provide an improved method for manufacturing plastic frameworks that includes forming two rectangular frameworks in a welding machine, then carrying out machining operations on these frameworks by one or more tools mounted in a processing machine, and then moving these frameworks to a weld cleaning machine where additional processing steps including weld cleaning steps are carried out.